The Effect of Different Morphologies of ZnO and Cr Doped ZnO NPs as Heterogeneous Catalyst for Biodiesel Production from Soybean Oil

In order to compensate for the reduction of fossil energy resources and to develop sustainable energy types and to help the environmental pollution crisis, biodiesel is introduced as one of the types of renewable biofuels that can be easily prepared and can be used without any changes in diesel engines. Biodiesel is one of the main biofuels that is usually produced from the catalyzed transesterification of fatty acids. Among the existing catalysts, zinc oxide (ZnO) is one of the best intermediate metal oxides that can be used in the production of biodiesel due to its high catalytic activity and environmental friendliness. In this research, different morphologies of zinc oxide in the form of nanoparticles (NPs), nanorods (NRs) and nanoflowers (NFs) were prepared as catalyst for transesterification of soybean oil with methanol were used. The reaction was carried out under optimal conditions at 65degree celsius with 6 wt% catalyst amounts at 30:1 methanol/oil molar ratio for 180 min, gave the biodiesel production conversion for NPs was 96.5% due to the largest surface area (10.61 m2/g) based on Brunauer Emmett Teller (BET) analysis, while the for NRs was 87.2% and for NFs was 44.6%. The catalyst is easily recovered after the reaction and reused, and after six stages the production conversion is reduced to 88.9%. Also, chromium (Cr) was doped with NPs and in the previous optimal conditions but in less reaction time (90 min), the conversion of 99.3% was obtained, and after six cycles of reuse of the catalyst, the production conversion is reduced to 91%. The prepared nanocatalysts were characterized using Fouier Transform Infrared (FTIR), X-Ray Diffractions (XRD), Energy Dispersive X-Ray (EDX), Scanning Electron Microscope (SEM), Inductively Coupled Plasma (ICP) and BET analyses. The Biodiesel production conversion was confirmed using Gas Chromatography (GC) analysis and the presence of methyl esters was confirmed using Gas Chromatography-Mass Spectrometry (GC-MS) analysis.